Oakland police officers made 44 percent fewer arrests last year than they had just three years before, city records show, a plunge in enforcement that extended from armed robbery cases to drug busts to minor crimes like public drunkenness.

That's 6,410 fewer arrests - an average of 18 fewer per day - in a city that has the highest crime rate in the state and, this year, is grappling with a 23 percent spike in murders, muggings and other major offenses.

The drop is so steep it has eased a backlog of cases in Alameda County Superior Court and may be contributing to a shrinking county jail population, officials said.

The arrest figures, obtained under the state's Public Records Act, raise questions about the effectiveness and assertiveness of the Police Department, which is struggling under the weight of job cuts, low morale and the demands of federal court oversight.

And there's no indication that the arrest totals for 2011 were an anomaly.

Arrest numbers were similar through July of this year - the last month included in data reviewed by The Chronicle. In October, Alameda County records show, Oakland police booked 459 arrestees at the Glenn E. DyerDetention Facility in Oakland, compared with 1,233 in October of 2008.

Criminologists and law enforcement experts said that while they would expect arrests to fall somewhat along with manpower, the trend was troubling. Nationally, arrests were down 11 percent in the same period, the FBI said.

"Obviously you can't arrest everybody, but if you're making good arrests and bringing good cases for prosecution, the word gets out and there's a snowball effect," said former San Francisco Police Chief Tony Ribera, who now teaches law enforcement leadership at the University of San Francisco.

"Conversely," he said, "if you're letting things go, and the people committing the crimes don't feel there are consequences, they are going to continue to do it."

Sgt. Chris Bolton, chief of staff to Police Chief Howard Jordan, who took his post in October 2011 following the resignation of Anthony Batts, said arrests were an important tool in crime-fighting but "not the sole answer."

Bolton said a lot of the proactive work that yields arrests - operations that target gangs and drug dealers, for instance - has fallen off as a result of job cuts. More than ever, he said, officers spend their time hustling from one emergency call to the next.

Due to layoffs and attrition, the force has 626 officers, a 25 percent decline from a high of 837 in December 2008. By comparison, San Francisco - which has twice the population of Oakland but 20 percent less violent crime - has 2,164 officers.

"In 2010, we said we needed at least 900 cops to be effective," Bolton said. "The first units to go when we faced staffing reductions were squads that were not tied to calls for service and were designed to address gangs, drugs and guns through proactive enforcement."

In a written statement, Mayor Jean Quan said, "We need to be taking more criminals off the streets, and tackling the problem requires both immediate and long-term solutions," including partnerships with outside agencies.

She said she would work to build the department back up to 800 officers in the next five years.

The plunge in arrests from 2008 to 2011 showed up in nearly every category.

The drop was 42 percent in robbery, 43 percent in drunken driving, 44 percent in weapons possession and 36 percent in domestic abuse. The starkest decrease came in drug manufacturing and dealing, where arrests plummeted 81 percent.

Separate police records show detectives are also solving fewer homicides, the department's top investigative priority.

The clearance rate for killings dropped from 50 percent in 2009 to 29 percent in both 2010 and 2011. The rate was 27 percent through October of this year, with seven cases resolved at once by the arrest of a man who went on a rampage at Oikos University in April.

Nationally, the homicide clearance rate is 65 percent, the FBI said.

Along International Boulevard in East Oakland, some residents and merchants said they believed a drop in policing had made the streets more dangerous.

"It's almost a free-for-all out here," said Robeson Perry, the 37-year-old owner of Famous One's Barber Shop. Criminals, he said, "figure they can get away with it. It's like a kid that tears the house up. If you let them, they are going to keep tearing the house up."

People are also frustrated in the Rockridge neighborhood. At Pegasus Books on College Avenue, employees said a store camera captured a longtime customer stuffing a pile of books into his pants in early September.

After the man tried to sell the books at a sister store in Berkeley, employees said, they called police and filed a report with a responding officer, offering up the suspect's name and address along with the video footage.

However, repeated efforts to call a theft detective to follow up failed, and the store finally gave up.

"We had someone dead to rights with a camera," said store owner Amy Thomas, whose employees haven't seen the customer since. "We did the real work of the case, and we haven't been able to get anyone to do anything about it."

Bolton said he would look into the case. He said that if the store delivered a suspect and solid evidence, "that is something that should have been done."

In Oakland, burglary and theft cases that lack such leads are not investigated, though they are tracked and mapped and can affect the way police deploy officers.

"Staffing levels have decreased to the point where, with the exception of homicide cases, only in-custody cases and a limited number of out-of-custody investigations assigned for follow-up are presented to the District Attorney's Office for charging," Rachal wrote.

Bolton said the department now has five officers investigating theft and fraud in a city that has seen almost 17,000 burglaries and car break-ins this year. He said 22 detectives were assigned to the more than 6,000 murders, robberies and aggravated assaults.

Recognizing the shortages, Bolton said, the department has sought to step up partnerships with outside agencies like the U.S. Marshals Service and the Bureau of Alcohol, Tobacco, Firearms and Explosives.

California Highway Patrol officers are now patrolling in East Oakland. And this week, City Council members Libby Schaaf and Larry Reid proposed spending $1.8 million to speed up the planned hiring of police officers, hire 20 civilians to help support the force, and temporarily bring Alameda County sheriff's deputies into Oakland.

Some veteran officers say the arrest data reflect not only a reduced workforce but also a form of "de-policing" under federal court oversight, which began 10 years ago after a police brutality scandal. The department must show it can track and control officers' conduct, and faces the threat of a federal takeover if it cannot.

The officers, who spoke on condition of anonymity, said the department's poor handling of the reform effort had caused some cops to shy away from aggressive work - confronting people who may be carrying guns or drugs, for example - because they want to avoid heavy paperwork and fear discipline from superiors if a suspect complains of abuse.

Chief Jordan, in a written statement, said the reform process added "administrative tasks to daily duties - duties that include an extraordinary demand for service and time." But he said the accountability measures benefit the department, its officers and the community.

John Burris, one of the civil rights attorneys whose lawsuit led to court oversight, said he was disturbed by the linking of the arrest rate to federal oversight. He said officers were well paid and should live up to their responsibilities.

He said the reform process "was never communicated to the officers in such a way as to get them to buy in and understand it wasn't a foreign way of policing, but a best-practices way of policing," Burris said. "I find these to be rationalizations, and not justifiable."

Burris added, "I have always been told by police practices experts that Oakland has a sufficient number of officers to do quality policing, but that it's a question of deployment."

Don Link, a 68-year-old Oakland resident who chairs the Shattuck Neighborhood Crime Prevention Council and supports the hiring of more officers, said police had shown they can impact crime through arrests. He cited recent cases in which officers captured teams of robbers targeting businesses.

"There are people that steal cars basically to use them for transportation from West Oakland to East Oakland," Link said. "I think all of these things build up to a sense, for the people who do crime, that it's an occupation, and that they can do it more or less with impunity."